Imitation windshields are garbage just like knock-off body panels. I'm certain that the copied, imported, Taiwanese, reverse-engineered, guesstimated glass weighs less than the genuine part from the OEM. (I've never weighed two pieces of glass, but the difference in body parts is quite apparent without even using a scale.)
Let's not dignify these parts by calling them "aftermarket", the way a tie rod end or a spark plug might innocuously be called "aftermarket".
Worst of all, the glass industry has taken to using the extremely confusing term "OEE", which apparently stands for "original equipment equivalent".
If you're looking for an angle to get your insurance company to pay for OEM glass, make sure to look it over very closely for imperfections; they're in there. Some people have actually had success complaining that the knock-off windshields don't have the same labelling on them: for example, the Ford windshields all say "SoundScreen" to denote their acoustic barrier.
Some people might scoff at the idea of demanding an OEM windshield, but it's actually part of the structure of a unibody vehicle. Its crash energy absorbing and diverting properties are designed to work in conjuction with the energy absorber, reinforcement bar, unibody rails, core support, airbag sensors, fenders, aprons, hood, hinge pillars, et cetera.
I've seen the cars that were fixed with imitation body parts, then had another minor front end accident. In the second accident, the airbags sometimes go off for no obvious reason. It's because the car's computers sense that the front structure is collapsing waaaay to fast, so it must be a catastrophic accident. It's really just because of the origami bumpers the insurance companies love so much. So really, I don't know if there's any money saved in the long run! Airbags are expensive...
[/rant]
